Soap and the Spanish for the same, jabón, sound like they have nothing in common. But sounds can be deceiving.
Both come from the same root: the Latin sebum, meaning “grease”.
How can such different words be so related? Easy: the Latin s- sound and its variations (sh‑, ch- and sy- for example) usually became, under the arabic influence, a j- sound in Spanish but remained more intact in English.
Thus, the s‑p of soap maps almost exactly to the j‑b of jabón. The “p” and “b” are often easily interchanged as well.
Less fun is also noting that, from the same Latin root, meaning “grease” we also get seborrhea (a medical condition of having too much grease on your skin).
One of our favorite patterns of sound change between English and Spanish is the sh/j shift: under the influence of arabic, many words that had a “s” or “sh” or “sy” or “ch” sound in Latin, started to be pronounced with the throat-clearing sound and written with a “j”. See sherry/jerez and chess/ajedrez or syrup/jarabe, for example.
Another example of this pattern is the Spanish word for “juice”, jugo. It comes from the Latin succus meaning, “juice” (particularly sap, or juice from plants).
From this Latin root succus we also get the English… suck.
Yes, if it sucks — it is juicy! Literally!
We can see the mapping in the s‑c to j‑g mapping. The “c” and “g” sounds are similar and often interchanged.
Interestingly, in Spain they do not say jugo to mean “juice”; instead, they say… suco. Suco, funnily enough, also comes from the same root of succus. It is just the variation that never underwent the arabic “j” transformation.
From the same root we also get the English succulent, although we do not get the superficially similar English juice, which comes from the Latin ius, meaning, “sauce.”
Enojar, Spanish for “to get angry”, has a fun cousin in the English, annoy.
Both of these (along with the French for “worldly boredom”, ennui) come from the Latin inodiare, meaning, “to hate”. The Latin in- adds emphasis to the odium, Latin for “hate”.
We can see the parallels in all with the open vowel, followed by the ‑n-, followed by a ‑y- sound, although in Spanish the ‑y- sounds (and its corresponding ‑x- and ‑sh- variations) often turned into the ‑j- sounds, as it did here. Thus, the a‑n-y maps to the e‑n-j.
Hatred, then, dissipates and weakens over time. In English, hatred weakens into mere annoyance. In Spanish, hatred weakens into just anger, enojo. And, best of all, hatred in French weakens into a world-weary boredom of ennui.
Embassy (and Ambassador) and its Spanish equivalent, Embajada (and Embajador), both come from the same ancestor, the Old French Ambactos.
What is most interesting about these two is that it is an example of the pattern where the ‑j- sound in Spanish maps to the ‑sh- sound (and its cousins, like ‑ss- and ‑ch-) in English. Remember syrup and jarabe, chess and ajedrez, sherry and jerez, and push and empujar for a few examples.
Thus, the m‑b-j of emabajada maps to the m‑b-ss of embassy.
Chief, and the Spanish for the same, Jefe, both come from the same root: the French chef, which means the same.
But this is odd as they sound so different! How are they related?
It’s not obvious, but it’s easy once you understand the pattern: The Latin sound “sh” and very similar sounds (such as the “ch” and “sy”) almost always became a “j” in Spanish. Like syrup and jarabe. Not obvious!